I just lost a colony this summer. They seemed fine in August. Then last week I noticed a yellow jacket coming out of the hive. So I opened it up and - not a bee in sight. All cells cleaned out.
Was that the wasps? There were not even any dead bees around.
Anyway, on the Roundup question... The plants with Roundup are DEAD. Bees don’t care about dead plants.
As I understand it, roundup gets into the roots of plants. What happens when it rains? Let's say that an orchard used roundup to kill weeds, and it got into the roots of the fruit trees. What if it didn't kill the trees but contaminated the fruit?
That was wasps for sure. They live in the ground, and raise their young in there. The wasp foragers hunt for honeybees and cut them in half, bringing the juicy part back to their underground nest to feed their young. The young produces some substance that affects the foragers, egging them on to more hunting. Quite a vicious cycle, made worse in the fall with slim food sources.
The remedies include making sure your hive entrance has been restricted by mid-August. I go to my smallest restrictor opening by September. Another remedy is hanging up wasp traps nearby your hives - there are directions online for making them using a soda bottle. Very simple, and effective - you wind up with a bottle of dead wasps.
On the roundup - when spraying, probably good to avoid flowering stuff.
On nicotinoids, hard to avoid - all seeds it seems these days are coated with the stuff, so a tiny amount gets into all parts of the plant, roots/stems/leaves/flowers/nectar/pollen.
What I’ve told is that many crops like corn now are genetically altered to tolerate glyphosate, so it can be sprayed over the whole field, leaving residue on the crops. The person who told me is convinced it’s the cause of many current health problems. Me, I try to keep an open mind.
“Anyway, on the Roundup question... The plants with Roundup are DEAD. Bees don’t care about dead plants.”
The intestinal flora in the bees are plants (bacteria and yeast). Roundup kills plants and intestinal flora. You can’t live without intestinal flora. Kill off the bees’ intestinal flora and the bees die.